Stapling machine



y 1966 D. VOLKMANN 3,251,276

STAPLING MACHINE Filed May 25, 1962 5 Sheets-Sheet 1 /NVEN To? TQILNESSMay 17, 1966 D. VOLKMANN STAPLING MACHINE 5 Sheets-Sheet 2 Filed May 25,1962 W wan W QUE RM file fer l/o/K man/7 ATTORNGjS May 17, 1966 D.VOLKMANN STAPLING MACHINE 5 Sheets-Sheet 5 Filed May 25, 1962 WEE DieterVo// man/7 GL M gm AT TDLNESS United States Patent 3,251,276 STAPLKNGMACHENE Dieter Volkmaun, Leinstrasse 23, Neustadt, Ruhenberge, GermanyFiled May 25, 1962, Ser. No. 199,560 3 Claims. (Cl. 91394) Thisinvention resides in the provision of a stapling machine to actuate, bypneumatic force, a piston on a work performing stroke.

A primary object of the invention is to provide a portable machineadapted to be connected to a supply of compressed air and which will,on' the actuation of the trigger of the machine, cause fastener means,such as wire staples, nails, pins and the like, to be driven into a workpiece from a magazine contained in the machine.

More specifically, an object of the invention is to a provide a manuallyportable pneumatic machine actuated by compressed air in that compressedair causes the working stroke of the piston as well as its returnmovement into the initial or starting position so that it is not anymore necessary to have a return spring for the piston.

In the case of stapling machines with pneumatic return of the pistonknown in the art, the piston is actuated upon by compressed air on bothsides, both during the Working stroke and during the return stroke. Inthis case, the compressed air is either reversed at the end of theworking stroke or it acts continuously on the piston which isconstructed as a stepped piston. The constructional length of themachine is however increased by the stepped piston which also exhibits agreater degree of recoil due to the increase in the piston mass, andthis is extremely disadvantageous with hand apparatus.

In another compressed air driven stapling machine, the air displaced bythe piston during the working stroke is stored, compressed in a specialchamber and is used for the return stroke of the piston. Thisair-storage chamber surrounds the cylinder concentrically an'd'thereforerequires an additional amount of space and 11 separate sealing means,thus increasing the dimensions and therewith also the weight and themanufacturing cost of the apparatus. Weight and space requirements must,however, be kept as small as possible with hand appliances in order topermit easy and convenient handling. Furthermore, the manufacturingcosts must be kept down. The hitherto known constructional types ofcompressed air-driven stapling machines do not fulfill theserequirements.

According to the invention a compressed air-driven stapling machine forfastening means is designed in such a manner that the disadvantages ofthe known constructional types of such appliances are obviated. For thispurpose, the invention provides the idea whereby whilst avoiding the useof a secondary chamber there is formed directly in the working cylinderon the side of the piston not acted upon by compressed air during theworking stroke and in the end position thereof, an air chamber which issealed oif relatively to the outer air, is connected with the compressedair supply and the pressure of which returns the piston, from theopposite side of which air has been released, into its starting posi-325L276 Patented May 17, 1966 tion. The construction of the staplingmachine according to the invention requires no supplementary space forthe return of the piston, on the contrary the space hitherto providedfor receiving the return spring is used for the pneumatic returnarrangement, so that the constructional height and diameter of theworking cylinder does not require to be increased, thus permitting asaving of weight and space which facilitates the handling of theapparatus.

In order that at the end of the working stroke of the piston a space maybe formed in the: cylinder which suffices for producing the returnforce, the invention furthermore provides means whereby the piston isretained in its end position at a specific distance from the cylinderbottom, simultaneously sealing: off the space thus formed relatively tothe outer air. This means may consist of an abutment disposed on thedriver and impinging on the cylinder bottom in the end position of thepiston, thereby sealing ofi" the ejection conduit guiding the driver.This abutment may simultaneously serve to space the piston in its endposition sufficently from the cylinder bottom to form a sufficientlylarge air chamber.

For retaining the piston at the necessary distance from the cylinderbottom and for sealing oil the air chambe formed thereby it is possible,in further development of the invention, also to provide two means whichare separate from each other. Thus, a sleeve like abutment having anaxial length corresponding to the size of the air chamber can bearranged on the cylinder bottom as a stroke limiting means for thepiston whereas the ejection conduit is closed by a valve-like elementprovided on the driver.

According to a further feature of the invention, there is provided onthe underside of the piston a sleeve which, in its end position, ensuresthe necessary spacing from the cylinder bottom and simultaneously alsoseals oil. the passage aperture of the driver.

The feed of compressed air into the air chamber formed in the endposition of the piston can be efiected in Various ways, for example bymeans of a passage formed in the end face of the piston, by means of anoverflow conduit formed in the inner wall of the cylinder or by means ofa clearance provided between the piston and the cylinder wall. By thismeans, there is produced at the end of the working stroke on theunderside of the piston a pressure which generates a return movementdisplacing the piston back into its starting position.

In order that the piston may have the necessary acceleration during itsworking stroke for producing a considerable impact force, the airdisplaced by it must be removed to the greatest possible extent. Sincethe driver, which generally consists of thin sheet-metal having thethickness of a wire staple hasonly a small degree of play in theejection conduit, offering a relatively considerable resistance to theescape of the air displaced by the piston it is advisable to keep thisresistance as small as possible by special means. For this purpose, thedriver can be formed with slots through which the air displaced by thepiston is able to escape to the exterior. It is also possible to providein the vicinity of the cylinder bottom a venting aperture, such as isconventional with apparatus provided, with return springs. This ventingaperture must be closed in the end position of the piston, in order thatthe pressure necessary for generating the recoil force is retained inthe air space. For the closing of the venting aperture, according to afurther feature of the invention, it is possible to provide a separateelement, i.e. a slide member which during the working stroke of thepiston frees the venting aperture and closes it in the end positionthereof. The said slide member is conveniently provided with a detentdevice which retains it during operation in a position freeing theventing aperture.

In its starting position, the piston is advantageously retained by aretaining device provided on the cylinder cover and consisting forexample of a mechanical locking means or a permanent magnet secured onthe cylinder cover and which retains the piston until the air flowinginto the compressed air feed conduit after the opening of thehand-actuated control valve has reached a sufficient pressure.

Further features of the invention will be apparent from the drawings,wherein various constructional examples of the subject of the inventionare illustrated. In the drawings:

FIGURE 1 shows a partial longitudinal section through a compressed airactuated hand apparatus for the driving ing of U-shaped staples,

FIGURE 2 shows a partial longitudinal section through another embodimentof a device of this kind,

FIGURE 3 shows a partial longitudinal section through still anotherembodiment, having a venting aperture controlled by a slide member,shown in the starting position of the piston,

FIGURE 4 shows a fragmentary longitudinal section of FIGURE 3 in theposition at the end of the working stroke of the piston,

FIGURE 5 shows the section illustrated in FIGURE 4, in a plane displacedthrough 90,

FIGURE 6 shows a partial longitudinal section through still anotherstaple driving apparatus with a separate spacing and sealing means.

Referring to FIGURE 1, the apparatus consists of a housing body 11designed as a handle member and provided with a stub pipe 12 forconnection to a source of compressed air. Formed in the housing body Illis a compressed air conduit 13 connected with an inlet valve 15' adaptedto be controlled by means of a trigger lever 14. The inlet valve 15 isconnected via a conduit 16 with the upper end of a cylinder 17 in whicha piston 18 is guided for sliding movement. The piston 18 is dished andthrough it extends a radial pin 19 upon which an appropriately boreddriver 2% is pushed, the central positioning of said driver beingassured by spacing sleeves 21 disposed on the pin 1% each of saidspacing sleeves bearing against a U-shaped sheet-metal element 22 pushedon the upper end of the driver 29. The two carrier members 22 hear attheir upper end against the inside of the dished piston 18 and areconnected at their other end with a disc 23.

The driver is guided in an ejection conduit 25 secured on the bottom 24of the cylinder 17 and con nected in known manner with a staple magazine26. Arranged on the cylinder bottom 24 is a cushioning means 27 made ofa resilient material such as rubber or the like and formed with anaperture 28 for the passage of the driver 20.

The valve 15 is formed in known manner with a venting duct 29 which,when the valve is closed, connects the duct 16 with the outer air.

Formed in the end face of the piston 18 is a bore 30 of small passagecross-section. The piston 18 which may for example be made of steel isretained in the starting position illustrated in the drawings by adisc-shaped permanent magnet 32 secured on the cylinder cover 31.

The mode of operation of the embodiment is as follows:

For driving a staple into a work piece, the trigger lever 14 is pivotedupwardly, whereby the inlet valve 15 is opened and the compressed airconduit 13 is connected with the air conduit 16, whereas the ventingconduit 29 is closed. The compressed air flows through the conduit 16into the upper portion of the cylinder I7 and moves the piston 18downwardly as soon as the pressure of the compressed air in the conduit16 overcomes the attraction force of the permanent magnet 32. During theworking stroke of the piston 13 a staple disposed in known manner in theejection conduit 25 is driven by the downwardly travelling striker 20into the work piece. The air displaced by the piston during its workingstroke flows for the greater part through the ejection conduit 25 intothe open air, since the driver 26 is guided therein with a certaindegree of play, so that the displaced air is practically speaking notcompressed and is unable to brake the downward movement of the piston13.

When the piston 18 has reached the end of its working stroke (thistaking place after a short time, of the order of some hundredths of asecond) the plate 23 impinges on the annular cushioning means 27 andcloses the outlet aperture of the driver 20 in air-tight manner. A smallpart of the compressed air acting on the upper end face of the piston 18passes during the working stroke to the lower side of the piston, in theend position of which (the inlet valve 15 still being open) an excesspressure is built up. As soon as the valve 15 reaches its closureposition due to cessation of the finger pressure on the trigger lever14, the venting duct 29 is opened and therewith the space over thepiston 18 is connected with the outer air by the conduit 16. Due to thespacing between the abutment plate 23 and the end face of the piston 18,it is possible for a pressure to 'build up under it, since the airchamber is sealed off by the abutment plate 23 at the point at which thedriver 20 extends through. This pressure suflices to return the piston18 out of its end position to the starting position, especially sincethe piston is not subjected to any counter-pressure during the returnstroke due to the fact that the venting conduit 29 is open. Thepermanent magnet 32 then retains the piston 18 in its starting positionuntil the cycle is repeated on the next opening of the inlet valve 15.

The bore 30 in the end face of the piston 18 requires only to have asmall cross-section, since the pressure necessary for the return forcebelow the piston is substantially smaller than the pressure of thecompressed air necessary for the working stroke. For this reason, verylittle or practically speaking no compressed air will flowduring theworking stroke through the bore 30 under the piston. If required, thebore 36 can be closed by a nonreturn valve, for example in the form of aplate fitted on the inside of the piston 18.

The embodiment illustrated in FIGURE 2 corresponds substantially to thatshown in FIGURE 1, except that in place of the dished piston 18 there isa solid piston 33, the underside of which carries a sleeve 34 connectedfirmly, for example, by welding, therewith and providing the necessaryspacing between the cylinder bottom 24- and the piston at the end of itsworking stroke. This tubular sleeve has a smaller diameter than thepiston 33 and is connected by a pin 35 with the driver 20 between whichand the sleeve 34 it is also possible to provide the spacer sleeves 21as illustrated in FIGURE 1, for retaining the driver in its middleposition.

In the path of travel of the piston 33 is a longitudinal conduit 36shown formed with cylinder wall 17 and connecting in the lower endposition of the piston 33 the side of the latter acted upon bycompressed air from the conduit 16 with the lower side of the piston 33.Compressed air flows through this return flow conduit 36 at the end ofthe working stroke into the lower air chamber and subjects the latter toa pressure which produces the recoil force for the return movement ofthe piston into its starting position.

At the end of the working stroke, the sleeve34 bears against thecushioning means 27 and thereby closes the outlet point of the driver 20in air-tight manner, so that the compressed air flowing throughtheoverflow conduit 36 into this air chamber is entirely made use of forproducing the return stroke.

In order to enlarge the bearing surface of the sleeve 34 and to dimiishthe Wear of the cushioning means 27, there may be provided at its lowerend a disc 37, as shown in broken lines in the drawings.

For the purpose of diminishing the recoil, the piston 33 can bemanufactured from light metal or plastic instead of from steel, in whichcase there is disposed on the upper end face, acted upon by compressedair, of the piston a disc of ferro-magnetic metal upon which thepermanent magnet 32 arranged in the cylinder cover 31 acts in thestarting position of the piston.

Whereas in the previously described constructional forms the airdisplaced by the piston during its working stroke in the cylinder flowsout to the open air through the ejection conduit 25, in the embodimentaccording to FIGURE 3, there is formed in the lower portion of thecylinder 17 a venting aperture 41 which is closed only for a short timeat the end of the working stroke of the piston 33. For this purpose, useis made of a slide plunger 42 which is sealed by an O-ring 43 relativelyto the inner wall of the cylinder 17. The slide plunger 42 is retainedby a detent device, for example a ball 45 subjected to the action of acompression spring 44 and snapping into an annular groove 46 in theinner wall of the cylinder, at a height such that its lower side isdisposed in the same radial plane as the upper edge of the ventingaperture 41. The side plunger 42 is formed with a recess 47 having alarger cross-section than the driver 20, so that the air displaced bythe piston 33 during the working stroke is able to escapeunhinderedthrough said recess 47 and the venting aperture 41 into the open air.Arranged at the upper side of the slide plunger 42 is a resilient insert48 against which the sleeve 34 of the piston 33 impinges in the endposition thereof, whereby the ball 45 snaps out of its annular groove 46and the slide plunger 42 is displaced into the end position illustratedin FIGURE 4 wherein it bears closely on the cushioning means 27 of thecylinder bottom 24 and simultaneously its recess 47 is sealed olf by thesleeve 34 of the piston 33. In this position, compressed air which haspassed through the inlet valve 15 (still open for a short time) and theair conduit 16 into the cylinder chamber above the piston 33, is able toflow through the overflow conduit 36 into the chamber (now closed) belowthe piston 33 and there to build up the pressure necessary for thereturn stroke of the piston, so

that the piston, after the closing of the inlet valve 15 andsimultaneously opening of the venting duct 29, again passes back intoits starting position.

In order that the slide plunger 42 may move out of the end positionillustrated in FIGURE 4 into the operative position illustrated inFIGURE 3, the driver 20 is, as shown in FIGURE 5, formed with a shoulder49 which lifts the slide plunger 42 during the return stroke of thepiston 33 to such an extent that the ball is able to snap into theannular groove 46 under the pressure of the spring 44.

as rubber or the like, serving as an abutment for the piston 33 in itslower end position and enclosing therewith an air chamber 52. The lengthof the cushioning member 51 in the axial direction is such that there isbuilt up by the compressed air reaching the lower side of the piston 33through the overflow conduit 36 at the end of the working stroke apressure which suifices for producing the return stroke of the piston.The said air chamber 52 is sealed off relatively to the ejection conduit25 by a widened portion 53 which is arranged at the upper end of thedriver 20 and the wedge-shaped transmission surfaces 54 of which bearagainst the recess 55 formed in the bottom of the cushioning member 51and seal off the said recess 55 in air-tight manner. The compressed airflowing in the end position of the piston 33 through the overflowconduit 36 into the chamber 52 is therefore unable to escape andproduces the recoil force necessary for returning the piston 33.

By means of the invention, the piston is reliably returned into itsstarting position by simple means and without using springs or sensitivereversing devices. In this connection, it is especially advantageousthat the cylinder does not require a. supplementary secondary chamberfor the air space providing the recoil force, the space otherwiseprovided for accommodating the return spring now being used for thepneumatic recoil of the piston. Thus, it is unnecessary to increase thedimensions of the apparatus so as to make provision for the pneumaticrecoil of the plunger, either in respect of constructional height or ofthe cylinder diameter.

The invention is of particular importance in connection with compressedair operated hand' appliances for the driving of staples and otherfastening means and has, in addition to the advantages of low weight andsmall dimensions, also that of lower manufacturing costs.

It is apparent that the examples shown above have been given solely byway of illustration and not by way of limitation and that they aresubject to many variations and modifications within the scope of thepresent invention. All such variations and modifications are to beincluded within the scope of the present invention.

I claim:

1. In a pneumatic stapling machine comprising a cylinder having a bottomand a slot extending through said bottom, a piston slidably supported insaid cylinder, a source of compressed air, means for admittingcompressed air from said source to one side of said piston, valve meansfor controlling the flow of air to said one side of said piston and forventing said flow, a staple driver for driving staples connected withthe other side of said piston and extending through said slot, said slotcommunicating with the atmosphere, resilient means limiting the workingstroke of said piston and establishing an air chamber at the other sideof said piston, said air chamber communicating with said slot and beingenclosed by said other side of the piston, said bottom of the cylinderand the adjacent walls of the cylinder; an overflow conduit located inthe wall of said cylinder and adapted to connect said air chamber with'said source at the end of the working stroke of said piston, the top ofsaid resilient means lying adjacent the bottom end of said overflowconduit, and a valve-like device disposed on said driver sealing saidslot from the atmosphere when said piston reaches the end of its workingstroke.

2. The stapling machine of claim 1 in which said stroke limiting meansconstitute a sleeve-like cushion which at the end of the working strokeof said piston encloses with the latter said air chamber which is sealedoff by said valve-like device disposed on said driver from said slot inwhich said driver is guided.

3. In a pneumatic stapling machine comprising a cylinder having a topand a bottom having an ejection conduit communicating with theatmosphere, a magnet mounted in the top of the cylinder, a pistonreciprocable in said cylinder and adapted to be retained by said magnetadjacent the top of the cylinder, means connected with said cylinder foradmitting compressed air into the top of said cylinder to the upper sideof said piston, valve means for controlling the flow of compressed airinto said cylinder and for venting said flow, a staple driver connectedwith the lower side of said piston and extending through said ejectionconduit for driving staples, said staple driver having a widened portionadapted to engage and seal said ejection conduit from the atmospherewhen said piston is in its stroke-end position, a resilient sleeve-likecushion mounted upon the bottom of said cylinder and enclosing with saidpiston an air chamber when the piston is in its stroke-end position,said cylinder having a Wale conduit interconnecting the upper side ofthe piston with said air chamber when the piston is in its strokeendposition the top of said resilient sleeve-Ike cushion lying adjacent thebottom end of said Wale conduit.

References Cited by the Examiner UNITED STATES PATENTS Slater 91399Moifett 915 Schafer 9l399 Juilfs 9146l X Wandel 914l6 10 SAMUEL LEVINE,Primary Examiner.

FRED E. ENGELTHALER, Examiner.

1. IN A PNEUMATIC STAPLING MACHINE COMPRISING A CYLINDER HAVING A BOTTOM AND A SLOT EXTENDING THROUGH SAID BOTTOM, A PISTON SLIDABLY SUPPORTED IN SAID CYLINDER, A SOURCE OF COMPRESSED AIR, MEANS FOR ADMITTING COMPRESSED AIR FROM SAID SOURCE TO ONE SIDE OF SAID PISTON, VALVE MEANS FOR CONTROLLING THE FLOW OF AIR TO SAID ONE SIDE OF SAID PISTON AND FOR VENTING SAID FLOW, A STAPLE DRIVER FOR DRIVING STAPLES CONNECTED WITH THE OTHER SIDE OF SAID PISTON AND EXTENDING THROUGH SAID SLOT, SAID SLOT COMMUNICATING WITH THE ATMOSPHERE, RESILIENT MEANS LIMITING THE WORKING STROKE OF SAID PISTON AND ESTABLISHING AN AIR CHAMBER AT THE OTHER SIDE OF SAID PISTON, SAID AIR CHAMBER COMMUNICATING WITH SAID SLOT AND BEING ENCLOSED BY SAID OTHER SIDE OF THE PISTON, SAID BOTTOM OF THE CYLINDER AND THE ADJACENT WALLS OF THE CYLINDER; OF THE CYLINDER AND LOCATED IN THE WALL OF SAID CYLINDER AND ADAPTED TO CON- 